The present disclosure provides a control process for operation of at least one valve of a gas supply system for a gas turbine and, in particular, a process allowing partial stroke tests. The present disclosure further provides a system for implementing this control process.
Gas supply systems are used in various industrial processes, such as for gas turbines. Gas supply systems for gas turbines are fitted with shut down devices that allow emergency stopping of a gas supply in order to ensure safety and/or maintenance. These shut down devices are generally rapid closure isolation valves that remain open or under control in normal operation. Regular tests on these isolation valves are necessary, as such valves tend to seize, which can lead to reliability problems during an emergency shutdown.
One method of testing these valves includes completely disconnecting the supply system from the gas turbines and executing a compete valve test. Alternatively, one can run partial stroke tests on the isolation valves in order to check their operation without disconnecting the supply system. Partial stroke tests (PST for “partial stroke test” in English) allow an operator to detect failures of a valve such as seizure or a mechanical blocking of the valve. These partial stroke tests allow the operator to increase the amount of time between complete valve tests, thereby increasing the period between the maintenance stops.
Various on-line tests on isolation valves have been proposed that prevent completely disconnecting the gas supply system. For example, in one partial closure test system on an isolation valve, a stroke of the valve is positioned in a predetermined intermediate position between a normal position and an emergency stop position. Such a partial closure test system can detect a loss of electric signal for controlling the valve and detect correct operation of the valve, such as by measuring a fluid pressure which controls an actuator.
Another method includes executing an on-line partial stroke test for an isolation valve. In addition to the isolation valve being tested, the gas supply system uses a second control and second isolation valve. The system includes a piping branch to bypass the isolation valve being tested in order to execute a complete closure test on the isolation valve being tested without disturbing the gas supply.
Partial closure on a line can cause transient phenomena, which creates disturbances upstream of the injectors of the gas turbine combustion chamber. These disturbances can disturb the turbine power level.